Turn off "Automatically adjust brightness." Turn off True Tone. Turn off Night Shift. Then you should have a stable monitor.

And yes, you do need about $10,000.00 worth of lab instruments to calibrate an Apple Studio Display. They do that at the factory for you, so you don't really have to recalibrate it. You just have to be sure all those "adaptive environmental controls" are defeated!

Work in a gray room, NO sunlight, ONE 60-Watt equivalent 5000K LED bounced off of a white ceiling in the corner behind the monitor. View prints under a 5000K LED bright enough to yield a gray card exposure of 1/100 at ISO 100 at f/10. Adjust monitor brightness to match print brightness. That should get you close.

If your prints are too dark (MOST common problem), then your monitor is too bright!

Okay, I just did EVERYTHING that you suggested. I also purchased a 5500K led lamp that sits in the far corner of my editing room that bounces off of my white ceiling. Now, should I leave the preset on, Photography (P3-D65) or put it back on the preset that was there from the factory which was, Apple Display (P3-600 nits)? I also lowered the monitor brightness to just below the mid point on the slider. I sent five test photos to White House Printing and at first I thought that the prints were a bit too dark and the colors were not a vibrant as what I saw on the monitor. So, I made some adjustments to the same photos and sent them back for more test prints. I need to say that the adjustments that I made to the second set of test photos were not the way that I usually edit. I am not a fan of over saturated colors at all but that is what I did in order to get the colors that I wanted in my prints, which was probably the wrong thing to do but I didn't know any better. I think what I will do is use my Canon Pro 100 instead of sending photos off for printing until I get the results that I want. Your opinion in this would be greatly appreciated.

Sidwalkastromony: I have an old Epson Stylus Pro 4880 that is on its last legs and I was thinking about getting the 8550 since I no longer do much photo business and 13x19 would be big enough. (I do use Epson Luster Pro paper for most of the things I print.) So, otherwise, how do you like the 8550?

I do a few headshots, some copywork, and some class reunions as far as paying work. Other than that I want to get into some macro work, maybe try photographing birds, and who knows what else. At 82 I just need something to do to stay active.

I love my ET 8550. I have had it for almost two years and I am still on the ink that came with the printer. I use it for greeting cards that I sell in my wife's jewelry booth at the local art walk in the summer. I also make prints for my own enjoyment, but except for the pigment black, the inks are not archival, therefore professional gallery prints are not really an option. I belong to the local arts alliance, and I may display a print or two in their gallery in the future, but mark them NFS (not for sale.) For prints, I like Moab lasal Exhibition Luster 300 with this printer, but it did not come with a profile, so I use the nearest built-in luster profile. For cards, I use Red River Polar Matte, which is profiled for this printer.